EP1360050B1

EP1360050B1 - Method to produce nasal and oral cannula breathing detection devices

Info

Publication number: EP1360050B1
Application number: EP01992093.3A
Authority: EP
Inventors: James N. Curti
Original assignee: Salter Labs Inc
Current assignee: Salter Labs Inc
Priority date: 2001-01-04
Filing date: 2001-12-12
Publication date: 2017-02-15
Anticipated expiration: 2021-12-12
Also published as: JP4170094B2; CA2433294C; CA2433294A1; EP1360050A1; US20030030183A1; US6830445B2; US6533984B2; JP2004523380A; US20020121729A1; AU2002232567B2; WO2002053346A1; EP1360050A4

Description

This invention provides a novel method of producing cannulas suitable for use in both nasal and oral applications, using disconnectable mandrel parts to form the mold over which cannula forming plastics material is applied to form the cannula.

BACKGROUND OF THE INVENTION

This invention relates generally to cannulas adapted for both mouth and nasal use to monitor breathing, in particular, a method of manufacturing a cannula adapted to interconnect with both nasal passages and the mouth for use to monitor breathing, especially for the detection of apnea.
Nasal cannulas are commonly used to administer gases, such as oxygen, to humans having respiratory problems. Illustrations of nasal cannulas used for this purpose are found in United States Patent No. 3,802,431 . Nasal cannulas have been used also for inhalation therapy, made possible by development of inhalation sensors such as described in United States Patent No. 4,745,925 . A nasal cannula can be used to monitor breathing and for detection of apnea (the absence of breathing) when connected to an inhalation sensor.
Nasal cannulas additionally adapted to communicate with the mouth of humans to permit administration of fluids or sensing of apnea during periods of mouth breathing or nasal blockage are also known.
The present invention is a novel method of manufacturing a cannula to communicate with both nasal and oral passages. This method provides in the preferred embodiment, disconnectable mandrels, which when assembled form a mold over which a cannula forming polymeric material is applied, and which, through the capability of being disconnected, each mandrel part from the other(s), facilitates removal of the mandrels from the formed cannula.
The prior art of dipping a part in a plastisol to create a coating thereof is exemplified by United States Patent Nos. 3,906,071 , 4,695,241 and 4,800,116 .
US 4106505 discloses a cannular having a body portion and a pair of nare formations, which is formed by dip moulding. The cannula disclosed in this specification does not however include a mouth piece. US4106505 does not include any details of the mandrel assembly used in the dip moulding process.
EP-A-0 933 094 discloses a cannula having a main body, first and second nares and a mouthpiece.
US-A-3 731 900 discloses a method of molding a nasal cannula using a unitary core or separate cores for the main body and the nasal tips.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a method of manufacturing cannulas using an assembly of disconnectable mandrels over which cannula forming polymeric material is applied. Application of the plastics material over the mandrel assembly and subsequent extraction of the mandrel sections following curing of the cannula material provides a finished cannula with contiguous internal flow paths to monitor a patent's breathing.
It is a further object of the invention to provide a multi-part mandrel assembly for forming a cannula which facilitates extraction of the mandrel assembly sections after at least partial curing the polymeric material forming the cannula.
Still another object of the invention is to form the main body forming mandrel as two separate, slightly spaced apart components which remain spaced apart from one another by a void, during the dipping process, so that the void becomes filled with a plastisol to form a septum or barrier which divides the internal passage into two compartments or passageways, one which facilitates the supply of supplemental oxygen to a patient while the other facilitates monitoring of the breathing of the patient.
According to the invention, there is provided a method of forming a cannula according to claim 1.
Also according to the invention there is provided a cannula mandrel assembly according to claim 9.
Preferred embodiments are defined in the dependent claims. Any embodiments, aspects and examples disclosed herein, but not falling under the scope of the claims, do not form part of the invention.

. BRIEF DESCRIPTION OF THE DRAWINGS.

. The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
. Fig. 1 is an orthogonal view of a cannula mandrel assembly with cannula forming polymeric material shown in ghost;
. Fig. 2 is an orthogonal view of the cannula mandrel parts prior to assembly;
. Fig. 3 is a side elevation of the mouthpiece mandrel of Figs. 1 and 2 showing an end connector;
. Fig. 4 is an end section of the end connector taken on section 4-4 of Fig. 3;
. Fig. 5 is a fragmentary side elevation of the main body mandrel of Figs. 1 and 2 taken in the direction of arrow 5 in Fig. 2;
. Fig. 6 is an elevation of the main body mandrel taken in the direction of arrow 6 in Fig. 5;
. Fig. 7 is a general cross-section of a cannula made by the method of the present invention taken in the direction of section 7-7 of Fig. 1;
. Fig. 8 is a flow diagram of the method of the present invention; and
. Fig. 9 is an orthogonal view of a cannula mandrel assembly for forming a septum or barrier in a void of the main body forming mandrel, with cannula forming polymeric material shown in ghost.

. DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring to Fig. 1, the main body forming mandrel 1 of a beryllium copper cannula mandrel assembly 3 is shown with nare forming mandrels 5 and 7, and a mouthpiece forming mandrel 9 with end connector 11, for joining the mouthpiece
mandrel 9 to the main body forming mandrel 1. Shown in ghost is a cannula formed on the assembly and comprising a main body 1', a pair of nares 5', 7'and a mouthpiece 9'composed of polyvinyl chloride (PVC).
Fig. 2 shows the mandrel assembly parts prior to assembly to produce the cannula mandrel assembly 3. Nare mandrels 5 and 7 have reduced diameter sections 13 and 15 to form nares 5', 7', respectively, over which cannula material is applied. Reduced diameter sections 13 and 15 of nare mandrels 5 and 7 mate slidably with blind holes 17 and 19 of main body mandrel 1. Main body mandrel 1 also has a rectangular recessed section 21 to slidably mate with end connector 11 of mouthpiece mandrel 9.
Nare mandrels 5 and 7 also have enlarged diameter sections 23 and 25 to support the mandrel in a jig. Additionally, the enlarged diameter enables sections 23 and 25 to provide a larger contact surface to provide grip for removal of nare mandrels 5 and 7 from main body mandrel 1 after partial curing of the PVC on mandrel assembly 3.
Fig. 2 further shows the mouthpiece mandrel 9 with the end connector 11 which has a slot 27 to slidably engage the rectangular section 21 of the main body mandrel 1. Slot 27 is sized to permit close contact of slot 27 with the rectangular section 21 of main body mandrel 1 such that a snug fit is obtained to removably retain the mouthpiece mandrel 9 on the main body mandrel 1 while facilitating extraction from rectangular section 21 following partial curing and cooling of the PVC. The outer surface of end connector 11 approximates the outer diameter of main body mandrel 1 to provide a uniform diameter of applied cannula material and to facilitate withdrawal of the mouthpiece mandrel 9 from the mouthpiece 9'of the canula.
Fig. 3 shows mouthpiece mandrel 9 having a desired radius X and end connector 11 with slot 27.
Fig. 4 shows the shape of end connector 11 and slot 27 through section 4-4 of Fig. 3.
Referring to Figs. 5 and 6, blind holes 17 and 19 are sized to mate slidably with reduced diameter sections 13 and 15 of the nare mandrels 5 and 7 in order to engage and support nare mandrels 5 and 7 during application of the PVC to form the cannula on the assembly 3. The rectangular section 21 is made with shoulder depth T removed to allow the diameter of end connector 11 of mouthpiece mandrel 9 to mate approximately flush with the diameter Y of main body 1.
Rectangular section 21 is shown with preferred relieving radii R at opposed ends of the section. Radius R may be omitted if main body mandrel 1 is machined or formed in a manner that allows this. Thickness Z of rectangular section 21 permits slot 27 of end connector 11 of mouthpiece mandrel 9 to firmly but slidably mate with rectangular section 21. Width W of rectangular section 21 is just sufficient to closely accommodate end connector 11 of mouthpiece mandrel 9.
Figs. 1 and 2 show nare mandrels 5 and 7 with bend sections. These bend sections direct the nares of the cannula into a patient's nasal cavities.
Although beryllium copper is the preferred material for the cannula mandrel assembly 3, other materials which possess appropriate working temperature ranges, retain dimensional stability for reuse in a manufacturing environment and which will release the cannula easily after curing of the PVC may be used. Metals including but not limited to the steels, aluminum, bronze, brass, and copper alloys may be used, as well as some plastics. Beryllium copper is preferred due to its ability to transfer heat rapidly and reliably release the cured plastics material of the cannula formed thereon. Rapid heat transfer is desirable for the mandrel material, both during heating cannula mandrel assembly 3 and following cannula material application, when a partial cure of the material is followed by rapid cooling.
Prior to application of a latex solution of PVC (plastisol) the cannula mandrel 3 is coated, usually by dipping, with a silicone release layer to facilitate removal of the mandrel from the plastisol to be applied. The application of the PVC in the preferred embodiment is by dipping the silicone coated cannula mandrel assembly 3 which has been heated in an oven at an oven temperature of from about 176.6°C (350°F) to about 290.6°C (550°F) (preferably about 232.2 °C (450°F)) for about 1 to about 3 minutes into a latex solution of PVC (plastisol). One or more dipping steps may be performed to achieve the desired finished cannula material thickness and each of these dipping steps may
be for 10-30 seconds. During dipping the mandrel is supported by the outer end portions of the nare mandrels.
The preferred use of a latex solution of PVC (plastisol) provides a semi-clear finished cannula with strength to withstand attachment of connectors and flexibility to prevent injury to the user. Alternatively, other plastics materials, which provide material properties suitable for this method, capable of forming a plastisol may be substituted for PVC.
Partial curing of the cannula takes place on the mandrel assembly 3. The cannula mandrel assembly with the partially cured PVC thereon is then placed in an oven a sufficient time for further curing at a temperature from about 210.0°C (410°F) to about 232.2°C (450°F). Following curing to stabilize the PVC and after the cannula has cooled sufficiently to allow mandrel removal with the assistance of the release layer, without damaging the cannula, while providing sufficient physical strength to retain cannula shape, the mandrel parts are removed from the cannula.
Using the inventive method, a cannula with two nares and a mouthpiece is formed as follows: a cannula mandrel assembly 3 is formed by first, slidably mating reduced diameter sections 13 and 15 of nare mandrels 5 and 7 with blind holes 17 and 19, respectively, of the main body mandrel1 ; second, orienting nare mandrels 5 and 7; third, slidably mating slot 27 of end connector 1-1 of the mouthpiece mandrel 9 with the rectangular section 21 of main body mandrel 1 in a desired orientation relative to nare mandrels 5 and 7; fourth, providing a silicone release layer substantially encompassing the mandrel; fifth, heating the assembled cannula mandrel assembly in an oven at a temperature of from about 176.6°C (350°F) to about 290.6°C (550°F); sixth, providing a liquid uncured latex PVC mix (plastisol); seventh, dipping the cannula mandrel assembly into the plastisol, at least once, until the desired material thickness on the assembly is achieved; eighth, at least partially curing the PVC at a temperature of about 210.0°C (410°F) to from about 232.2°C (450°F); and ninth, removing the nare mandrels 5 and 7 from the blind holes 17 and 19 of main body mandrel 1 and the nares 5', 7' by pulling on enlarged diameter sections of nare mandrels 5 and 7, removing mouthpiece mandrel 9 from the mouthpiece 9' by disconnecting slot 27 of end connector 11 from rectangular section 21 of main body mandrel 1 and pulling
the mouthpiece mandrel 9 through the mouthpiece 9'; and finally slidably removing main body mandrel 1 from the main body 1' of the cannula.
Fig. 7 show a finished cannula, following removal of cannula mandrel assembly 3 parts from the cured PVC, showing contiguous flow paths through the main body 1', nares 5' and 7' and mouthpiece 9'.
It will be appreciated that the curing step may be completed in two stages, a first partial cure of the PVC produced by the heated cannula mandrel assembly 3 sufficient to maintain the PVC on this assembly and a second step in an oven at the above curing temperatures to complete the curing of the PVC.
It will be further appreciated that the outer ends of the main body 1' may be trimmed to provide a discrete area where connecting tubing may be connected thereto, e.g. by solvent bonding, and that the mouthpiece may be trimmed to a length suited to an individual patient so as to maximize the sensitivity of the finished device.
It will also be understood that disassembly of the cannula mandrel assembly, following cannula material cure, can proceed by removing the mouthpiece mandrel before the nare mandrels as obvious alternative method steps, prior to removal of the main body mandrel.
One modification of the present invention relates to the addition of a septum in the internal passage of the cannula to provide a barrier therein. The septum 29 divides the internal passage into two compartments or passageways so that a first one of the nares 5' can be coupled to an oxygen source (not shown) to facilitate the supply of supplemental oxygen to one of the nostrils of a patient while the other one of the nares 7' and the central mouthpiece 9' can be coupled to a monitoring device (not shown), such as a transducer, to facilitate monitoring of breathing of the patient or coupled to a demand oxygen conserving device (not shown) while the patient, at the same time, is still able to receive, either continuously or intermittently during the sensed breathing cycle, a supply of oxygen.
To manufacture the septum 29, the main body forming mandrel 1 is formed as first and second separate, slightly spaced apart components 30,31 which remain spaced apart from one another by a void 32 during the dipping operation of the manufacturing process so that the void 32 between the first and second separate, slightly spaced apart components 30, 31 is filled with the plastisol to form the septum 29. Once the cannula is cured, the septum 29 forms a barrier which divides the internal passage into two compartments or passageways.
Following sufficient curing, the nare mandrels 5 and 7 are removed from the blind holes 17 and 19 of main body mandrel 1 and the nares 5', 7' by pulling on enlarged diameter sections of nare mandrels 5 and 7, the mouthpiece mandrel 9 is removed from the mouthpiece 9' by disconnecting slot 27 of end connector 11 from rectangular section 21 of main body mandrel 1 and pulling the mouthpiece mandrel 9 through the mouthpiece 9'; and the first and second spaced apart components 30, 31 of the main body mandrel 1 are removed from the main body 1' of the cannula by pulling the first and second spaced apart components 30, 31 axially away from one another.

This variation of the manufacturing process is suitable for intermittent nocturnal oxygen delivery even though the patient breaths through his or her mouth.

Reference numerals

1	main body mandrel	19	blind hole
1'	main body	21	rectangular recessed section
3	cannula mandrel assembly	23	enlarged diameter section
5	nare mandrel	25	enlarged diameter section
5'	nare mandrel	27	slot
7	nare mandrel
7'	nare	R	radius
9	mouthpiece mandrel	T	rectangular section shoulder depth
9'	mouthpiece	T	rectangular section shoulder depth
11	end connector	W	rectangular section width
13	reduced diameter section	X	mouthpiece mandrel radius
15	reduced diameter section	Y	main body diameter
17	blind hole	Z	rectangular section thickness

Claims

A method of forming a cannula comprising the steps of providing parts for forming a cannula mandrel assembly (3), the parts comprising a pair of nare forming mandrels (5, 7) each defining an end,
a main body forming mandrel (1) having a rectangular central recessed section (21) and openings (17, 19) to receive and engage the ends of the nare forming mandrels (5, 7), and a mouthpiece forming mandrel (9) having an end connector (11), the end connector (11) defining a slot (27) dimensioned to mate slidingly with the central recessed section (21);

assembling the parts to form the cannula mandrel assembly (3) defining interior spaces of the cannula to be formed; heating the cannula mandrel assembly (3) to a desired temperature;

providing an uncured cannula forming polymeric material in a flowable state;

dipping the heated cannula mandrel assembly (3) in the polymeric material to form a desired thickness of partially cured polymeric material on the cannula mandrel assembly (3) for forming the cannula;

heating the partially cured polymeric material on the cannula mandrel assembly (3) to further cure the polymeric material; and

extracting, from the cured polymeric material, the nare forming mandrels (5, 7), the mouthpiece forming mandrel (9) by removing the slot (27) from the rectangular central recessed section (21), and the main body forming mandrel (1) to produce the cannula.
A method according to claim 1 characterized in that the main body forming mandrel comprises separate first and second components with a void (32) formed therebetween, said rectangular central recessed section (21) being formed in one of the first and second components and an opening being formed in each said first and second components to receive and engage the end of one of the n are forming mandrels (5, 7).
A method according to claim 1 or 2 characterized in that the cannula mandrel assembly (3) is manufactured from beryllium copper.
A method according to any one of the preceding claims characterized in that the cannula mandrel assembly (3) is heated to a temperature of from about 176.6°C (350°F) to about to about 290.6°C (550°F).
A method according to any one of the preceding claims characterized in that the cannula mandrel assembly (3) is coated with a layer of release material prior to dipping in the polymeric material.
A method according to any one of the preceding claims characterized in that the polymeric material is applied by a plurality of dipping steps.
A method according to any one of the preceding claims characterized in that the polymeric material is at least partially cured at a temperature of from about 210.0°C (410°F) to about 232.2°C (450°F).
A method according to any one of the preceding claims characterized in that the end connector (11) of the mouthpiece mandrel (9) is provided with an outer surface about the slot (27) having a dimension which is the same as a main dimension of the main body portion to ensure that the nasal cannula is formed having a substantially constant inner diameter.
A cannula mandrel assembly (3), defining the interior cavity of a cannula having a main body, first and second nares and a mouthpiece, the cannula mandrel assembly (3) comprising a main body forming mandrel (3) and a pair of nare forming mandrels (5', 7'),
the main body forming mandrel (3) defines openings for releasably engaging the nare forming mandrels (5', 7'), the mandrel assembly (3) also comprising an elongate mouthpiece forming mandrel (9) having an end connector (11) defining a slot (27),
the main body forming mandrel (1) also defining a central recessed rectangular section (21) slidably receiving, engaging and supporting the end connector slot (27) of the mouthpiece forming mandrel (9); and
the main body forming mandrel (3) comprises two separate components (1, 31).
A cannula mandrel assembly (3) according to claim 9 characterized in that the two separate components (1, 31) define a void (32) therebetween for forming a septum (29).
A cannula mandrel assembly (3) to claim 10, characterized in that the recessed rectangular section (21) is provided in one of the two components and each component is provided with and opening for one of the nare forming mandrels.